NO. O COMPARATIVE HISTOLOGY OF FEMUR FOOTE 105 



extended for some distance between the lamime. Tlie lacuaa^ of all iinils are 

 well developed. 

 Type II-III, C. 



FEMUR OF ALCES MACHLIS. ELK. CE. MED. COLL. 



Pl. 11, Fig. 205. Syn. Tab. V 



' Antero-posterior diameter of bone, 35 mm. ; lateral, .33 mm. 



Antero-posterior diameter of medullary canal, 23 mm. ; lateral, 20 mm. 



The medullary canal is full. Medullary index, 66%. 



Structure. — A ring of external circumferential lamellse surrounds the bone. 

 Their lacunae are long and narrow and their canaliculi are long and branching. 

 The central ring, constituting the greater part of the bone, is composed of fully 

 developed lamina? separated by concentric canals and interrupted at short 

 intervals by completely developed Haversian systems. The laminae are fre- 

 quently transected by the canals, which freely communicate with each other. 

 They are composed of lamellae with long, narrow lacunae and branching cana- 

 liculi. They have the appearance of a strong development. The canals are 

 wide and in some places have widened into Haversian canals. 



The Haversian systems have long, narrow lacunae and long branching cana- 

 liculi. The Haversian canals are large, round or oval in shape, and freely com- 

 municate with each other. Beginning in the posterior wall, and extending 

 around the outer wall, nearly to the anterior mid-line, and occupying a position 

 next to the internal circumferential lamellae, is a narrow zone of Haversian 

 systems. Another grouji is found near the surface of the anterior wall, and 

 near the medullary canal are several large vascular canals surrounded by 

 lamellae. 



Type II-III, C. 



RIGHT FEMUR OF CAMELUS. CAMEL. XO. 35379, AMER. MUS. NAT. HIST. 



Pl. 11, Fig. 206. Syn. Tab. V 



Antero-posterior diameter of bone, 51 mm. ; lateral, 50 mm. 



Antero-posterior diameter of medullary canal, 35 mm. ; lateral, 35 mm. 



The medullary canal is full. Medullary index, 93%. 



Structure. — The section is composed of concentric lamina crossed by numer- 

 ous canals. Their lacunae are oval and long and their canaliculi are bushy and 

 straight. Near the medullary border the laminae are interrupted by numerous 

 irregularly shaped spaces. The posterior ridge is composed of Haversian 

 systems of the (lb) dit¥erentiatiou. Around the medullary surface these are 

 separated by large, irregularly shaped spaces. 



Type II-III, lb. 



